Using the RPM package from Zabbix repository, zabbix-proxy does not start

Text from /var/log/message
Starting Zabbix Proxy...
zabbix_proxy : zbx_option requires an argument – c
zabbix_proxy: usage: zabbix_proxy [-hV] [-c <file>] [-R <option>]

Have to edit /usr/lib/systemd/system/zabbix-proxy.service

Environment value was set wrongly (zabbix-proxy.conf instead of zabbix_proxy.conf).
Service still not start-able after changing above value

In the end, change to
ExecStart=/usr/sbin/zabbix_proxy -c /etc/zabbix/zabbix_proxy.conf